Users subscribed to the services provided by a telecommunications system are usually assigned to identifiers (subscriber identifiers, subscriber identities, or subscriber-IDs). For a given subscription of a user in a given telecommunication system, at least one subscriber-ID is used to be assigned. Said subscriber-ID(s) identify uniquely said subscription and is used in said system for addressing and identification purposes. The type, content, and even the number of subscriber-ID(s) per user, depends basically on the characteristics of the telecommunications system.
For instance, in a telecommunications systems such as a Public Switch Telephone Network (PSTN) or Integrated Services Digital Network (ISDN), users are assigned to one telephone number as subscriber-ID (although more than one telephone number can be assigned per user in said systems). These telephone numbers are according to the format specified in ITU-T recommendation E.164 (May 1997), and are assigned per user according to a specific numbering plan. Once an E.164 number is assigned to a user of a PSTN, said number is used both: for addressing (routing) calls to said user, and also to identify said user within the network. Since in this kind of wired systems the point in the telecommunications system where the user access to the service said system provides (the access point) is fixed, the user is supposed to be reachable in the terminal connected to said access point and, therefore, the user is usually not forced to register (attach) prior to get access to the services provided by the telecommunications system.
In other telecommunications system, such as for instance in a 2G (second generation) mobile system (such as a Global System for Mobile communications, or GSM), or in a 3G (third generation) mobile systems (also known as Universal Mobile Telecommunications System, or UMTS), said subscriber-ID is not unique per user. A given user subscribed to one of said 2G or 3G systems is assigned to a unique private identifier (private identity or private-ID) and to, at least, one public identifier (public identity or public-ID).
Also, as opposite to traditional telecommunications systems using fixed (wired) access technologies (e.g.: PSTN), in mobile systems the same user can access to said system from different access points; i.e.: from different locations. Due to this, said user register his/her presence from a different access point in a given moment (e.g.: each time from the same or different terminal through the same or different radio access server); therefore, the user registers (attach) his/her presence in a given access point from a given terminal prior to access to further services, such as make or receive calls. Within said process (hereinafter referred as registration), the user's terminal identifies the subscription he/she holds and wants to activate, and this is accomplished by sending (among other authentication and identification data) the private-ID associated to said subscription.
Once the registration of a 2G or 3G user has run successfully, said user can receive incoming sessions (e.g.: voice calls) on his/her terminal from other users that have “dialled” the public-ID (or one of the public-IDs) associated to said subscription of said user. I.e.: the public-ID is utilized by other users as an aforementioned “telephone number”.
At this point, it shall be noticed that the term “session”, whenever cited within this invention, encompasses various kind of communications that, according to the state-of-the-art telecommunication systems and telecommunication protocols, can be established between communication peers; thus, being not limited to traditional “voice calls” provided by well known circuit-switched based systems and protocols, but also comprising communications provided by packet-switched (or cell-switched) based systems and protocols, that provides communications with multiple media capabilities, such as audio, video and data, even simultaneously within the same communication. Examples of said communications, known as “multimedia communications” (also as “multimedia sessions” or “multimedia calls”), are described, for instance, in ITU-T recommendation H.323 (November 2000), or in IETF's RFC-2543 “Session Initiation Protocol”, SIP (March 1999).
For a given subscription of a given user in a 2G or 3G system, a given home server in the system (known as Home Location Register or HLR, or Home Subscriber Server or HSS.) keeps, among other data, and as a part of the SD (subscriber data) related to said subscription, the relationship between said subscription of said user and the private-ID and public-ID(s) associated to it. Said home servers (for example HLRs or HSSs) are mainly in charge of attending request from other nodes or servers within the system whenever a registration request of a given user needs to be attended (i.e.: granted or rejected), or whenever location information of a given user is needed (e.g.: at call to said user).
In 2G or 3G systems, the private-ID of a given user is unique per user subscription and it is used within the 2G or 3G system for internal identification purposes at registration, authorization, administration, etc.
For a given subscription, said private-ID is also stored in a subscriber identity module known for example as SIM, or USIM for 3G, which is included in the subscriber's card for example a Subscriber Identity Module card or SIM card, or UMTS Integrated Circuit card or UICC, provided to said user, together with other security information related to said subscription such as secret keys used for authentication. Said subscriber's card (SIM card, UICC) is intended to be accommodated, either: fixed or removable, in user's terminals used for accessing said systems.
Unlike Public-IDs, Private-IDs does not need to be known by the users of said systems, nor known by other users of other telecommunications systems, since they are not intended to be supplied (i.e.: “dialled”) by a given user for establishing a communication with another user; i.e.: said private-IDs are not intended to be used as “called number”, nor intended for identifying the calling or connected party in the end user terminal display.
In 2G systems, a private-ID takes the format of IMSI (International Mobile Subscriber Identity); while in 3G systems, a private-ID takes the form of a NAI (Network Access Identifier) as defined in RFC-2486 “The Network Access Identifier” (January 1999), wherein the IMSI can be contained within the NAI.
In said 2G or 3G systems, the public-ID(s) of a given user is, however, intended for addressing (routing) calls to said user, and, therefore, intended to be used as “telephone numbers” are in other telecommunication systems for example PSTN (Public Switched Telephone Network), ISDN (Integrates Services Digital Network), including calling and connected party identification purposes. So, public-IDs are used for establishing communications between users, and, therefore, intended to be known by the users, not only of said mobile systems (2G or 3G), but also by users of other telecommunications systems which can interwork with said 2G or 3G systems. In this way a user (user-A) who wants to establish a communication with another user (user-B) needs to supply (i.e.: to “dial”) the public-ID of said user-B (or one of the public-IDs of said user-B) in the call request said user-A makes. User-B, in turn, can (if said service is allowed) identify the calling party from the public-ID of user-A said user-B receives.
The format of the public-ID(s) of a given user can vary depending on the particularities of the telecommunications system said user is subscribed. In 2G and 3G systems, public-IDs are in the format of E.164 numbers (known as MSISDN numbers) (i.e.: they are typical telephone numbers such as in PSTN). In 3G systems that implements the so called IM Subsystem (or IMS) (Internet Protocol Multimedia Subsystem), said public-IDs can also take another formats, such as SIP-URL (Uniform Resource Locator for Session Initiation Protocol), TEL-URL (Uniform Resource Locator for telephony), etc.
Given that current mobile systems (2G or 3G) do only provide one private-ID per user subscription, and given that said unique private-ID is used in the registration process, said systems does not permit a given user to register into a mobile system referencing the same subscription (i.e.: by identifying the same private-ID on each registration request) from more than one terminal, since it would imply the existence of a SIM cloning situation, meaning the existence of two subscription cards with the same data on them. Therefore (and regardless various complex techniques for SIM cloning detection), if a given user tries to register and already has a registration active for his/her subscription, said new registration is considered a re-registration and all data related to the old registration are overwritten with the data related to the new one.
With this situation, for a given user having only one subscription, only one registration can be active for said user and said single subscription, and no simultaneous locations are allowed for said single subscription. In this way, a given user who wants to have more than one terminal registered, has to hold more than one subscription and use a different subscription for registering each of said terminals.
Modern telecommunication systems (such as 3G mobile systems) are, however, intended to offer a huge variety of services. Depending on the nature of said services, some of them would require some capabilities within the end-user terminal (e.g.: a service based on multimedia capabilities or file/data transfer capabilities) not needed for other services (e.g.: a service based on mere voice capabilities).
This, would make desirable for a given user having one subscription in one of said systems to be registered from a plurality of terminals simultaneously (e.g.: having different capabilities each); and all this, without harming security aspects that rely on the identification of the subscription of said user nor forcing to said user to hold more than one subscription.
FIG. 1 has been taken from the technical specification TS 23.228 (V5.0.0, April 2001) released by the 3GPP (3rd Generation Partnership Project), which is the forum in charge of developing the standards ruling the 3G systems. Although this figure shows the relationship between private-ID and public-ID(s) of a given subscription (Internet Multimedia subscription, or IM-subscription) of a given user (IM-user) of the IMS (Internet Protocol Multimedia Subsystem) of a 3G system; it actually shows the state-of-the-art univocal relationship existing in mobile systems regardless its generation (2G or 3G) between one subscription and the private-ID associated to said subscription. Within said figure, it can be observed that, even though a given user holding a single subscription can be reached (i.e.: called) by means of different public-IDs, the subscription of said user is identified by a single (and only) private-ID.
The relationship shown in FIG. 1 is maintained and held primarily in the home server of said user (HSS, HLR), although copies of said data and relationships can also be kept and used in other nodes (or servers) within the telecommunications system. However the logic inherent to the aforementioned univocal relationship is deployed across any server within the telecommunication system, thus disabling both: to have multiple active registrations of a given user holding a single subscription from a plurality of access points, and to have subsequent calls addressed to said user to be delivered to one or more of said of access points where said user can be located.
Known standards for 3G systems have regarded the possibility of having UMTS subscriber cards holding more than one subscription (i.e.: more than one USIM within the same UICC) (e.g.: 3GPP TS 22.101, v4.0.0, June 2001), thus allowing the same terminal to be registered alternatively for different user subscriptions. However, only one of these subscription can be active in a given moment in said terminal, and, in any case, the capabilities inherent to said terminals related to the kind of sessions it can handle remains the same regardless the active subscription.
SIP (Session Initiation Protocol) was selected by 3GPP as the protocol for handling user registrations and session control for users holding IM-subscriptions. The specification of SIP (RFC-2543) already allows a given user to indicate in a registration message REGISTER multiple contact points where said user can be contacted (i.e.: reached) for further incoming sessions addressed to the identity (i.e.: public-ID) contained in the “From” header or said REGISTER message. These contact points are included in subsequent “Contact” headers within one or subsequent REGISTER messages, wherein each “Contact” header contains an address of a given SIP endpoint (i.e.: a SIP enabled terminal). According to this, a SIP REGISTER message from a given user such as:                REGISTER sip:server2.wcom.com        Via: . . .        From: <sip:UserB@there.com>        To: . . .        Call-ID: . . .        CSeq: 1 REGISTER        Contact: <sip:UserB@110.111.112.113>        Contact: tel:+1-972-555-2222        Content-Length: . . .        
if accepted by the registration server “server2.wcom.com”, would make that further sessions addressed to said user (i.e.: further INVITE messages indicating in the “To” header the identity “UserB@there.com”) are forwarded simultaneously to both contact points that were specified in the REGISTER message: the SIP application in host with IP-Addr (Internet Protocol address) 110.111.112.113 where said user has logged in as “UserB”, and to the telephone number “+1-972-555-2222”.
However, the adaptation and use of the SIP protocol to the specific architecture of IMS in 3G systems has blocked said possibility, as it can be seen in the 3GPP specification that states the signaling flows for IM-users (TS 24.228, V1.0.0, June 2001). In said specification it is stated that the content of the “Contact” header must be the IP-Addr said terminal is using to access to the 3G system (i.e. the IP-address said terminal got during the process it ran to get a radio bearer packet-based, known as PDP (Packet Data Protocol) Context Establishment process); that is to say, the address it uses to exchange packets with the server which is serving its access to the system.
With this limitation, a given user holding a single IM-subscription in a 3G system, can have only one registration active at the same time, said registration being related to only one access point to the system and to only one terminal attached to said access point and identified by a single address (IP-Addr).
Therefore, according to the state-of-the-art, a given user who would like to have multiple active registrations in any of said mobile systems (2G, 3G) that requires to manage information related to the location of said user for any of those registrations, as well as to manage information related to the identifiers that address and identify said user in said system, would be forced to hold different subscriptions. However, since each individual subscription is held separately in said systems, thus implying separate processing and administration (i.e.: separate accounting records, separate subscription records, separate location data, etc.) it would imply difficulties for the mobile system operator for allowing the same public-ID(s), related to the same user, to be assigned to more than one subscription; no mention to inconvenience for the user, having to deal with multiple bills for the same service.
It should be then desirable a situation wherein, without having to appeal to a solution based on multiple subscriptions per user, a given user having a single subscription in a telecommunications system (such as a mobile system, or other telecommunications system of similar characteristics regarding user identities and location information), is allowed to register into said system from different terminals simultaneously, thus having multiple registrations active simultaneously; and wherein said user can receive calls in any of these registered terminals from other parties that have “dialled” one public-ID that is associated to said single subscription.